Cardiovascular System PDF

Cardiovascular system KRISTLE ANN JUDAVAR DMD-1A What is Cardiovascular system? The cardiovascular system is one of the most important processes in the body. Also referred to as the circulatory system or vascular system, the cardiovascular system is an essential component of maintaining homeostasi...

Cardiovascular system KRISTLE ANN JUDAVAR DMD-1A What is Cardiovascular system? The cardiovascular system is one of the most important processes in the body. Also referred to as the circulatory system or vascular system, the cardiovascular system is an essential component of maintaining homeostasis, a state of balance among systems of the body, by circulating blood. When it comes to understanding your heart health, it’s important to be familiar with the parts of the cardiovascular system and how the system works. WWW.PULSEHVVI.COM/PARTS-OF-THE-CARDIOVASCULAR-SYSTEM/ Cardiovascular system The cardiovascular system (cardio- = heart; vascular = blood or blood vessels) consists of three interrelated components: blood, the heart, and blood vessels. The branch of science concerned with the study of blood, blood- forming tissues, and the disorders associated with them is hematology (hema- or hemato- = blood; -logy = study of). GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION  Blood Blood contributes to homeostasis by transporting oxygen, carbon dioxide, nutrients, and hormones to and from your body’s cells. It also helps regulate body pH and temperature, and provides protection against disease through phagocytosis and the production of antibodies. Blood transports various substances, helps regulate several life processes, and affords protection against disease. For all of its similarities in origin, composition, and functions, blood is as unique from one person to another as are skin, bone, and hair. Health-care professionals routinely examine and analyze its differences through various blood tests when trying to determine the cause of different diseases. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Functions of Blood Blood has three general functions: 1. Transportation. As you just learned, blood transports oxygen from the lungs to the cells of the body and carbon dioxide from the body cells to the lungs for exhalation. It carries nutrients from the gastrointestinal tract to body cells and hormones from endocrine glands to other body cells. Blood also transports heat and waste products to various organs for elimination from the body. 2. Regulation. Circulating blood helps maintain homeostasis of all body fluids. Blood helps regulate pH through the use of buffers (chemicals that convert strong acids or bases into weak ones). It also helps adjust body temperature through the heat-absorbing and coolant properties of the water (see Section 2.4) in blood plasma and its variable rate of flow through the skin, where excess heat can be lost from the blood to the environment. In addition, blood osmotic pressure influences the water content of cells, mainly through interactions of dissolved ions and proteins. 3. Protection. Blood can clot (become gel-like), which protects against its excessive loss from the cardiovascular system aft er an injury. In addition, its white blood cells protect against disease by carrying on phagocytosis. Several types of blood proteins, including antibodies, interferons, and complement, help protect against disease in a variety of ways. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Components of Blood Whole blood has two components: (1) blood plasma, a watery liquid extracellular matrix that contains dissolved substances, and (2) formed elements, which are cells and cell fragments. If a sample of blood is centrifuged (spun) in a small glass tube, the cells (which are more dense) sink to the bottom of the tube while the plasma (which is less dense) forms a layer on top.. Blood is about 45% formed elements and 55% blood plasma. Normally, more than 99% of the formed elements are cells named for their red color—red blood cells (RBCs). Pale, colorless white blood cells (WBCs) and platelets occupy less than 1% of the formed elements. Because they are less dense than red blood cells but more dense than blood plasma, they form a very thin buff y coat layer between the packed RBCs and plasma in centrifuged blood. Figure 19.1b shows the composition of blood plasma and the numbers of the various types of formed elements in blood. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION  Blood Vessels Another essential part of the cardiovascular system is the blood vessels, which are tubes that transport blood throughout the body. There are so many blood vessels in the body that if you laid the average adult’s out in a line, the line would be close to 100,000 miles long. Based on their function, blood vessels are classified as either arteries, veins, or capillaries. Arteries carry blood from the heart to the body, and veins carry blood from the body to the heart. Capillaries are extremely narrow, microscopic blood vessels that connect arteries and veins. www.pulsehvvi.com/parts-of-the-cardiovascular-system/  Structure and Function of Blood Vessels The five main types of blood vessels are arteries, arterioles, capillaries, venules, and veins. Arteries carry blood away from the heart to other organs. Large, elastic arteries leave the heart and divide into medium-sized, muscular arteries that branch out into the various regions of the body. Medium- sized arteries then divide into small arteries, which in turn divide into still smaller arteries called arterioles. As the arterioles enter a tissue, they branch into numerous tiny vessels called blood capillaries or simply capillaries. The thin walls of capillaries allow the exchange of substances between the blood and body tissues. Groups of capillaries within a tissue reunite to form small veins called venules. These in turn merge to form progressively larger blood vessels called veins. Veins are the blood vessels that convey blood from the tissues back to the heart. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Basic Structure of a Blood Vessel The wall of a blood vessel consists of three layers, or tunics, of different tissues: an epithelial inner lining, a middle layer consisting of smooth muscle and elastic connective tissue, and a connective tissue outer covering. The three structural layers of a generalized blood vessel from innermost to outermost are the tunica interna (intima), tunica media, and tunica externa (adventitia). Modifications of this basic design account for the five types of blood vessels and the structural and functional differences among the various vessel types. Always remember that structural variations correlate to the differences in function that occur throughout the cardiovascular system. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION The tunica interna forms the inner lining of a blood vessel and is in direct contact with the blood as it flows through the lumen, or interior opening, of the vessel (Figure 21.1a, b). Although this layer has multiple parts, these tissue components contribute minimally to the thickness of the vessel wall. Its innermost layer is called endothelium, which is continuous with the endocardial lining of the heart. The endothelium is a thin layer of flattened cells that lines the inner surface of the entire cardiovascular system (heart and blood vessels). The tunica media is a muscular and connective tissue layer that displays the greatest variation among the different vessel types. In most vessels, it is a relatively thick layer comprising mainly smooth muscle cells and substantial amounts of elastic fibers. The primary role of the smooth muscle cells, which extend circularly around the lumen like a ring encircles your finger, is to regulate the diameter of the lumen. An increase in sympathetic stimulation typically stimulates the smooth muscle to contract, squeezing the vessel wall and narrowing the lumen. Such a decrease in the diameter of the lumen of a blood vessel is called vasoconstriction. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION  Tunica Externa The outer covering of a blood vessel, the tunica externa (externa = outermost), consists of elastic and collagen fibers. The tunica externa contains numerous nerves and, especially in larger vessels, tiny blood vessels that supply the tissue of the vessel wall. These small vessels that supply blood to the tissues of the vessel are called vasa vasorum, or vessels to the vessels. They are easily seen on large vessels such as the aorta. In addition to the important role of supplying the vessel wall with nerves and self-vessels, the tunica externa helps anchor the vessels to surrounding tissues. major initial branches, such as the brachiocephalic, subclavian, common carotid, and common iliac arteries. Elastic arteries perform an important function: They help propel blood onward while the ventricles are relaxing. As blood is ejected from the heart into elastic arteries, their walls stretch, easily accommodating the surge of blood. As they stretch, the elastic fibers momentarily store mechanical energy, functioning as a pressure reservoir. Then, the elastic fibers recoil and convert stored (potential) energy in the vessel into kinetic energy of the blood. Thus, blood continues to move through the arteries even while the ventricles are relaxed. Because they conduct blood from the heart to medium sized, more muscular arteries, elastic arteries also are called conducting arteries. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Arteries Because arteries were found empty at death, in ancient times they were thought to contain only air. The wall of an artery has the three layers of a typical blood vessel, but has a thick muscular-to- elastic tunica media (Figure 21.1a). Due to their plentiful elastic fibers, ar teries normally have high compliance, which means that their walls stretch easily or expand without tearing in response to a small increase in pressure. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Elastic Arteries Elastic arteries are the largest arteries in the body, ranging from the garden hose–sized aorta and pulmonary trunk to the finger-sized branches of the aorta. They have the largest diameter among arteries, but their vessel walls (approximately one-tenth of the vessel’s total diameter) are relatively thin compared with the overall size of the vessel. These vessels are characterized by well-defined internal and external elastic laminae, along with a thick tunica media that is dominated by elastic fibers, called the elastic lamellae. Elastic arteries include the two major trunks that exit the heart (the aorta and the pulmonary trunk), along with the aorta’s major initial branches, such as the brachiocephalic, subclavian, common carotid, and common iliac arteries (see Figure 21.20a). Elastic arteries perform an important function: They help propel blood onward while the ventricles are relaxing. As blood is ejected from the heart into elastic arteries, their walls stretch, easily accommodating the surge of blood. As they stretch, the elastic fibers momentarily store mechanical energy, functioning as a pressure reservoir(Figure 21.2a). Then, the elastic fibers recoil and convert stored (potential) energy in the vessel into kinetic energy of the blood. Thus, blood continues to move through the arteries even while the ventricles are relaxed (Figure 21.2b). Because they conduct blood from the heart to medium sized, more muscular arteries, elastic arteries also are called conducting arteries. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Muscular Arteries Medium-sized arteries are called muscular arteries because their tunica media contains more smooth muscle and fewer elastic fibers than elastic arteries. The large amount of smooth muscle, approximately three quarters of the total mass, makes the walls of muscular arteries relatively thick. Thus, muscular arteries are capable of greater vasoconstriction and vasodilation to adjust the rate of blood flow. Muscular arteries have a well-defined internal elastic lamina but a thin external elastic lamina. These two elastic laminae form the inner and outer boundaries of the muscular tunica media. In large arteries, the thick tunica media can have as many as 40 layers of circumferentially arranged smooth muscle cells; in smaller arteries there are as few as three layers. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Anastomoses Most tissues of the body receive blood from more than one artery. The union of the branches of two or more arteries supplying the same body region is called an anastomosis. Anastomoses between arteries provide alternative routes for blood to reach a tissue or organ. If blood flow stops for a short time when normal movements compress a vessel, or if a vessel is blocked by disease, injury, or surgery, then circulation to a part of the body is not necessarily stopped. The alternative route of blood flow to a body part through an anastomosis is known as collateral circulation. Anastomoses may also occur between veins and between arterioles and venules. Arteries that do not anastomose are known as end arteries. Obstruction of an end artery interrupts the blood supply to a whole segment of an organ, producing necrosis (death) of that segment. Alternative blood routes may also be provided by nonanastomosing vessels that supply the same region of the body. Arterioles Literally meaning small arteries, arterioles are abundant microscopic vessels that regulate the flow of blood into the capillary networks of the body’s tissues (see Figure 21.3). The approximately 400 million arterioles have diameters that range in size from 15 μm to 300 μm. The wall thickness of arterioles is one-half of the total vessel diameter. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Capillaries Capillaries, the smallest of blood vessels, have diameters of 5– 10 μm, and form the U- turns that connect the arterial outflow to the venous return (Figure 21.3). Since red blood cells have a diameter of 8 μm, they must often fold on themselves in order to pass single file through the lumens of these vessels. Capillaries form an extensive network, approximately 20 billion in number, of short (hundreds of micrometers in length), branched, interconnecting vessels that course among the individual cells of the body. This network forms an enormous surface area to make contact with the body’s cells. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Venules Unlike their thick-walled arterial counterparts, venules and veins have thin walls that do not readily maintain their shape. Venules drain the capillary blood and begin the return flow of blood back toward the heart. As noted earlier, venules that initially receive blood from capillaries are called postcapillary venules. They are the smallest venules, measuring 10 μm to 50 μm in diameter, and have loosely organized intercellular junctions (the weakest endothelial contacts encountered along the entire vascular tree) and thus are very porous. They function as significant sites of exchange of nutrients and wastes and white blood cell emigration, and for this reason form part of the microcirculatory exchange unit along with the capillaries. Veins While veins do show structural changes as they increase in size from small to medium to large, the structural changes are not as distinct as they are in arteries. Veins, in general, have very thin walls relative to their total diameter (average thickness is less than one-tenth of the vessel diameter). They range in size from 0.5 mm in diameter for small veins to 3 cm in the large superior and interior venae cavae entering the heart. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION  Heart The heart acts as the pump that makes the circulation of blood – and the oxygen and nutrients blood carries – to all tissues of the body possible. If the heart stops pumping for even a few minutes, it cannot deliver blood to the rest of the body, putting the individual’s life in danger. www.pulsehvvi.com/parts-of-the-cardiovascular-system/ Heart In terms of structure, the heart has two sides and is divided into four chambers: the left atrium, the right atrium, the left ventricle, and the right ventricle. The thin-walled atria receive blood from the veins, and the thick- walled ventricles pump blood out of the heart. On the left and right sides of the heart, the atrium and ventricle work together to pump blood through and out of the heart. Both sides of the heart work simultaneously to promote blood flow. On the left, blood flows from the lungs to the atrium and then the ventricle, which pumps it into the rest of the body. On the right side, blood flows from the rest of the body into the atrium, then the ventricle, which pumps the blood into the lungs. Valves between the chambers of the heart ensure blood flows in the correct direction. Veins also contain valves to maintain blood flow into the heart. Arteries don’t need valves, as the pressure of blood flow from the heart is enough to keep blood flowing in the correct direction. www.pulsehvvi.com/parts-of-the-cardiovascular-system/ For blood to reach body cells and exchange materials with them, it must be pumped continuously by the heart through the body’s blood vessels. The heart beats about 100,000 times every day, which adds up to about 35 million beats in a year, and approximately 2.5 billion times in an average lifetime. The left side of the heart pumps blood through an estimated 100,000 km (60,000 mi) of blood vessels, which is equivalent to traveling around the earth’s equator about three times. The right side of the heart pumps blood through the lungs, enabling blood to pick up oxygen and unload carbon dioxide. Even while you are sleeping, your heart pumps 30 times its own weight each minute, which amounts to about 5 liters (5.3 qt) to the lungs and the same volume to the rest of the body. At this rate, your heart pumps more than about 14,000 liters (3600 gal) of blood in a day, or 5 million liters (1.3 million gal) in a year. You don’t spend all of your time sleeping, however, and your heart pumps more vigorously when you are active. Thus, the actual blood volume your heart pumps in a single day is much larger. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Location of the Heart The scientific study of the normal heart and the diseases associated with it is known as cardiology (kar-dē-OL-ō-jē; cardio- = heart; -logy = study of).For all its might, the heart is relatively small, roughly the same size (but not the same shape) as your closed fist. It is about 12 cm (5 in.) long, 9 cm (3.5 in.) wide at its broadest point, and 6 cm (2.5 in.) thick, with an average mass of 250 g (8 oz) in adult females and 300 g (10 oz) in adult males. The heart rests on the diaphragm, near the midline of the thoracic cavity. Recall that the midline is an imaginary vertical line that divides the body into unequal left and right sides. The heart lies in the mediastinum, an anatomical region that extends from the sternum to the vertebral column, from the first rib to the diaphragm, and between the lungs (Figure 20.1a). About two-thirds of the mass of the heart lies to the left of the body’s midline (Figure 20.1b). You can visualize the heart as a cone lying on its side. The pointed apex is formed by the tip of the left ventricle (a lower chamber of the heart) and rests on the diaphragm. It is directed anteriorly, inferiorly, and to the left. The base of the heart is opposite the apex and is its posterior aspect. It is formed by the atria (upper chambers) of the heart, mostly the left atrium (see Figure 20.3c). In addition to the apex and base, the heart has several distinct surfaces. The anterior surface is deep to the sternum and ribs. The inferior surface is the part of the heart between the apex and right surface and rests mostly on the diaphragm (Figure 20.1b). The right surface faces the right lung and extends from the inferior surface to the base. The left surface faces the left lung and extends from the base to the apex. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Pericardium The membrane that surrounds and protects the heart is the pericardium. It confines the heart to its position in the mediastinum, while allowing suffcient freedom of movement for vigorous and rapid contraction. The pericardium consists of two main parts: (1) the fibrous pericardium and (2) the serous pericardium (Figure 20.2a). The superficial fibrous pericardium is composed of tough, inelastic, dense irregular connective tissue. It resembles a bag that rests on and attaches to the diaphragm; its open end is fused to the connective tissues of the blood vessels entering and leaving the heart. The fibrous pericardium prevents overstretching of the heart, provides protection, and anchors the heart in the mediastinum. The fibrous pericardium near the apex of the heart is partially fused to the central tendon of the diaphragm and therefore movement of the diaphragm, as in deep breathing, facilitates the movement of blood by the heart. The deeper serous pericardium is a thinner, more delicate membrane that forms a double layer around the heart (Figure 20.2a). The outer parietal layer of the serous pericardium is fused to the fibrous pericardium. The inner visceral layer of the serous pericardium, which is also called the epicardium, is one of the layers of the heart wall and adheres tightly to the surface of the heart. Between the parietal and visceral layers of the serous pericardium is a thin film of lubricating serous fluid. This slippery secretion of the pericardial cells, known as pericardial fluid, reduces friction between the layers of the serous pericardium as the heart moves. The space that contains the few milliliters of pericardial fluid is called the pericardial cavity. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Chambers of the Heart The heart has four chambers. The two superior receiving chambers are the atria, and the two inferior pumping chambers are the ventricles. The paired atria receive blood from blood vessels returning blood to the heart, called veins, while the ventricles eject the blood from the heart into blood vessels called arteries. Each auricle slightly increases the capacity of an atrium so that it can hold a greater volume of blood. Also on the surface of the heart are a series of grooves, called sulci, that contain coronary blood vessels and a variable amount of fat. Each sulcus marks the external boundary between two chambers of the heart. The deep coronary sulcus encircles most of the heart and marks the external boundary between the superior atria and inferior ventricles. The anterior interventricular sulcus is a shallow groove on the anterior surface of the heart that marks the external boundary between the right and left ventricles on the anterior aspect of the heart. This sulcus continues around to the posterior surface of the heart as the posterior interventricular sulcus, which marks the external boundary between the ventricles on the posterior aspect of the heart (Figure 20.3c). GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Right Atrium The right atrium forms the right surface of the heart and receives blood from three veins: the superior vena cava, inferior vena cava, and coronary sinus (Figure 20.4a). (Veins always carry blood toward the heart.) The right atrium is about 2–3 mm (0.08–0.12 in.) in average thickness. The anterior and posterior walls of the right atrium are very different. The inside of the posterior wall is smooth; the inside of the anterior wall is rough due to the presence of muscular ridges called pectinate muscles, which also extend into the auricle (Figure 20.4b). Between the right atrium and left atrium is a thin partition called the interatrial septum (inter- = between; septum = a dividing wall or partition). A prominent feature of this septum is an oval depression called the fossa ovalis, the remnant of the foramen ovalis, an opening in the interatrial septum of the fetal heart that normally closes soon aft er birth (see Figure 21.31). Blood passes from the right atrium into the right ventricle through a valve that is called the tricuspid valve because it consists of three cusps or leaflets (Figure 20.4a). It is also called the right atrioventricular valve. The valves of the heart are composed of dense connective tissue covered by endocardium. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION Right Ventricle The right ventricle is about 4–5 mm (0.16–0.2 in.) Left Ventricle The left ventricle is the thickest chamber of in average thickness and forms most of the anterior surface of the heart, averaging 10–15 mm (0.4–0.6 in.), and forms the the heart. The inside of the right ventricle contains a series of apex of the heart. Like the right ventricle, the left ventricle ridges formed by raised bundles of cardiac muscle fibers called contains trabeculae carneae and has chordae tendineae trabeculae carneae. The cusps of the tricuspid valve are that anchor the cusps of the bicuspid valve to papillary connected to tendon like cords, the chordae tendineae, which in muscles. Blood passes from the left ventricle through the turn are connected to cone-shaped trabeculae carneae called aortic valve (aortic semilunar valve) into the ascending papillary muscles. Internally, the right ventricle is separated from aorta (aorte = to suspend, because the aorta once was the left ventricle by a partition called the interventricular septum. believed to lift up the heart). Some of the blood in the Blood passes from the right ventricle through the pulmonary aorta flows into the coronary arteries, which branch from valve (pulmonary semilunar valve) into a large artery called the the ascending aorta and carry blood to the heart wall. The pulmonary trunk, which divides into right and left pulmonary remainder of the blood passes into the arch of the aorta arteries and carries blood to the lungs. Arteries always take blood and descending aorta (thoracic aorta and abdominal away from the heart (a mnemonic to help you: artery = away). aorta). Branches of the arch of the aorta and descending aorta carry blood throughout the body. During fetal life, a temporary blood vessel, called the ductus arteriosus, Left Atrium The left atrium is about the same thickness as the shunts blood from the pulmonary trunk into the aorta. right atrium and forms most of the base of the heart. It receives Hence, only a small amount of blood enters the blood from the lungs through four pulmonary veins. Like the right nonfunctioning fetal lungs. The ductus arteriosus normally atrium, the inside of the left atrium has a smooth posterior wall. closes shortly aft er birth, leaving a remnant known as the Because pectinate muscles are confined to the auricle of the left ligamentum arteriosum, which connects the arch of the atrium, the anterior wall of the left atrium also is smooth. Blood aorta and pulmonary trunk. passes from the left atrium into the left ventricle through the bicuspid (mitral) valve (bi- = two), which, as its name implies, has two cusps. GERARD J. TORTORA BRYAN DERRICKSON Principles of Human Anatomy & Physiology 15e and WileyPLUS with ORION